Perry Lassiter wrote:Related to the slang "flunk" meaning to fail, esp a test or course in school? And why flunk OUT?

There doesn't appear to be any connection between "flunkey" and "flunk". It seems the latter is derived from old British slang funk (fear or panic) and/or flinch. My guess is that it was first used to mean "avoid or discontinue a task through fear", "fail a test of character" (hence "flunk out"), and then shifted to mean "fail an academic test".